(1) Field of the Invention
The present invention relates to a segment of a film strip having a flexible beam lead frame formed thereon, to which an integrated circuit (IC) chip is adapted to be bonded in a wireless manner, and also relates to a holder or fixture for holding the film segment with the IC chip, wherein the film segment can be positioned to test the IC chip at a given test position with respect to the fixture.
(2) Description of the Related Art
In the fabrication of an IC device, it is well known that an IC chip is bonded in a wireless manner to a flexible beam lead frame formed on a segment of a film strip, and also that such a film segment with the IC chip is detachably held by a holder or fixture to prevent the IC chip from being polluted or being damaged during handling and shipping thereof, as disclosed, for example, in U.S. Pat. No. 4,007,479 issued on Feb. 8, 1977, U.S. Pat. No. 4,069,496 issued on Jan. 17, 1978 (Re. 30,604 reissued on May 5, 1981), and U.S. Pat. No. 4,547,794 issued on Oct. 15, 1985.
In order to produce a film segment having a flexible beam lead frame formed thereon, a plurality of flexible beam lead frames are continuously formed or bound as a thin layer of a suitable electrical conductor such as copper, nickel, aluminum, or the like on a long film strip of a flexible material, which has the general appearance of a strip of motion picture film with sprocket perforations located along the lateral edges thereof, and then the long film strip is cut into segments so that each segment includes at least one lead frame.
When the film segment is held by the fixture, some of the sprocket perforations thereof are utilized so that the film segment is disposed in place with respect to the fixture. In particular, the fixture has some protrusions which are adapted to be inserted into some of the sprocket perforations located along the lateral edges of the film segment. By inserting the protrusions into the sprocket perforations, the film segment is held in place by the fixture. Note that since the protrusions are loosely inserted into the sprocket, the film segment is somewhat movable with respect to the fixture.
While the film segment is held by the holder, the IC chip bonded thereto is tested by electrically contacting pin-like probes to terminals or conductor pads of the lead frame, which are located on the film segment at closely spaced points. In testing, the film segment must be precisely positioned at a given test position with respect the fixture held at a fixed position, so that all of the pin-like probes can be properly contacted to the pads of the lead frame. Of course, unless proper contacts can be obtained between the pin-like probes and the pads, respectively, it is impossible to adequately carry out the test.
Some of the sprocket perforations of the film segment are also utilized to position the film segment at the given test position. In particular, the fixture has at least two access openings formed therein, which are aligned with two sprocket perforations of the film segment which are located along the lateral edges thereof, respectively, and which are not occupied by the protrusions used to hold the film segment by the fixture. By inserting two positioning pin elements into these sprocket perforations through the access openings, the film segment is positioned at the given test position with respect to the fixture, with the fixture being supported in a fixed position.
However, utilization of the sprocket perforations of the film segment should be avoided for the reason that high precision may be expected in positioning the film segment at the given test position. In particular, when the plurality of flexible beam lead frames are continuously formed or bound on the long film strip, and when the long film strip is cut into film segments, the long film strip is fed by engaging the sprocket perforations thereof with drive sprockets, in the same way as a motion picture film is driven. Thus, the film edges forming the sprocket perforations of the film strip may be subjected to plastic deformation due to the engagement of the perforation with the sprockets. This is because it is not expedient to utilize the sprocket perforations of the film segment for the positioning of the film segment at the given test position.
In addition, when the positioning pin elements are inserted into the sprocket perforations of the film segment through the access openings of the fixture, the film segment may be resiliently deflected. This is because the film segment is loosely held by the fixture, and because the sprocket perforations of the film segment which are located along the lateral edges thereof are spaced apart from the conductor pad zone by a distance great enough to cause the film segment to be resiliently deflected. Of course, deflection of the film segment decreased the positioning precision.